U.S. patent number 7,212,929 [Application Number 11/144,647] was granted by the patent office on 2007-05-01 for moisture data-acquiring device and image-forming apparatus.
This patent grant is currently assigned to Canon Kabushiki Kaisha. Invention is credited to Norio Kaneko, Takehiko Kawasaki.
United States Patent |
7,212,929 |
Kaneko , et al. |
May 1, 2007 |
**Please see images for:
( Certificate of Correction ) ** |
Moisture data-acquiring device and image-forming apparatus
Abstract
A moisture data-acquiring device has a force-applying unit for
applying an external force to a sheet, a force-receiving unit for
receiving the external force through the sheet, a signal outputting
unit for outputting a signal reflecting a mechanical property of
the sheet which unit is placed on at least one of the
force-applying unit and the force-receiving unit, and a moisture
data-acquiring unit for acquiring data on moisture of the sheet
based on the signal from the signal outputting unit.
Inventors: |
Kaneko; Norio (Atsugi,
JP), Kawasaki; Takehiko (Atsugi, JP) |
Assignee: |
Canon Kabushiki Kaisha (Tokyo,
JP)
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Family
ID: |
35449056 |
Appl.
No.: |
11/144,647 |
Filed: |
June 6, 2005 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20050271403 A1 |
Dec 8, 2005 |
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Foreign Application Priority Data
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Jun 7, 2004 [JP] |
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2004-169114 |
May 18, 2005 [JP] |
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2005-146036 |
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Current U.S.
Class: |
702/50 |
Current CPC
Class: |
G01N
19/10 (20130101); G01N 33/346 (20130101); G03G
15/5029 (20130101); G01N 2203/0005 (20130101); G01N
2203/0078 (20130101); G01N 2203/0282 (20130101) |
Current International
Class: |
G01N
3/32 (20060101) |
Field of
Search: |
;702/50 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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5-118984 |
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May 1993 |
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JP |
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5-164690 |
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Jun 1993 |
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JP |
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2000-156834 |
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Jun 2000 |
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JP |
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Primary Examiner: Nghiem; Michael
Assistant Examiner: Khuu; Cindy D.
Attorney, Agent or Firm: Fitzpatrick, Cella, Harper &
Scinto
Claims
What is claimed is:
1. A moisture content-acquiring device for acquiring data on
moisture contained in a sheet, comprising: a force-applying unit
for applying an external force to the sheet; a force-receiving unit
for receiving the external force through the sheet; a signal
outputting unit for outputting a signal reflecting a mechanical
property of the sheet, which signal outputting unit is placed on at
least one of the force-applying unit and the force-receiving unit,
and which output signal is acquired through application of the
external force; and a moisture content-acquiring unit for acquiring
data on moisture of the sheet based on the signal from the signal
outputting unit, which moisture content-acquiring unit acquires the
moisture content of the sheet by a comparison of the signal
acquired through application of the external force from the signal
outputting unit with data stored in a memory, the data on a
relation between a moisture content in the sheet and the signal
from the signal outputting unit.
2. The moisture data-acquiring device according to claim 1, wherein
the force-applying unit applies the external force plural times to
the sheet.
3. The moisture data-acquiring device according to claim 1, wherein
a position-defining means is provided for defining the position of
the sheet to keep a constant distance between the force-receiving
unit and the sheet.
4. The moisture data-acquiring device according to claim 1, wherein
the force-applying unit applies an external force to the sheet to
bend and bring the sheet into contact with the force-receiving
unit, and the contact causes output of the signal from the signal
outputting unit.
5. The moisture data-acquiring device according to claim 1, wherein
the sheet is bent from the position of the sheet before the contact
with the force-receiving unit by a concave or a groove provided on
a side of the sheet on which the force-receiving unit is
located.
6. An image-forming apparatus, comprising the moisture
data-acquiring device set forth in claim 1 and an image forming
assembly for forming an image on a sheet, wherein a condition for
image formation is adjusted based on the data from the moisture
content-acquiring device.
7. An image-forming apparatus, comprising the moisture
data-acquiring device set forth in claim 1, an image forming
assembly for forming an image on a sheet and a delivery means for
delivering the sheet, wherein a condition for delivering sheet are
adjusted based on data from the moisture content-acquiring device.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a moisture data-acquiring device
(a water content information-acquiring apparatus), and an
image-forming apparatus.
2. Description of Related Art
Moisture-measuring devices are known as apparatuses for acquiring
information on moisture such as a water content in a sheet material
like recording paper sheets and postcards.
An example of the moisture-measuring device is an optical apparatus
which determines the moisture content in a sheet material by
measuring light absorption or light reflection.
The optical type device isolates light of the absorption wavelength
1.94 .mu.m of water, and light of plural reference wavelengths from
continuous spectrum light, for example, by a spectroscope or a wave
filter, and measures the water content by comparison of absorbance
or reflectivity of the light by water with those of the reference
light (e.g., Japanese Patent Application Laid-Open Nos. H05-164690,
and H05-118984).
Otherwise, a technique using a monochromatic light is disclosed to
avoid use of a spectroscope or a wave filter not to enlarge the
apparatus (e.g., Japanese Patent Application Laid-Open No.
2000-156834).
SUMMARY OF THE INVENTION
The above conventional optical type of moisture-measuring device
requires essentially optical parts such as a light source, a light
detector, and a spectroscope or filter. Further, the optical type
of moisture-measuring device can be affected by dust from the sheet
material or the like to cause variation of sensitivity of the
photodetector. Therefore, a new type of moisture data-acquiring
device is wanted.
The present invention intends to provide a device for acquiring
information on the moisture in a sheet material, different from the
aforementioned optical type apparatus.
According to an aspect of the present invention, there is provided
a moisture data-acquiring device for acquiring data on moisture
contained in a sheet, comprising: a force-applying unit for
applying an external force to the sheet; a force-receiving unit for
receiving the external force through the sheet; a signal outputting
unit for outputting a signal reflecting a mechanical property of
the sheet which unit is placed on at least one of the
force-applying unit and the force-receiving unit; and a moisture
data-acquiring unit for acquiring data on moisture of the sheet
based on the signal from the signal outputting unit.
The force-applying unit preferably applies the external force
plural times to the sheet.
In the moisture data-acquiring device, a position-defining means is
preferably provided for defining the position of the sheet to keep
a constant distance between the force-receiving unit and the
sheet.
The moisture data-acquiring unit preferably acquires the data on
moisture of the sheet by the comparison of the signal from the
signal outputting unit with data memorized in a memory on the
relation between data on moisture of the sheet and signals from the
signal outputting unit.
The force-applying unit preferably applies an external force to the
sheet to bend and bring the sheet into contact with the
force-receiving unit, and the contact causes output of the signal
from the signal outputting unit. The sheet is preferably bent from
the position of the sheet before the contact with the
force-receiving unit by a concave or a groove provided on a side of
the sheet on which the force-receiving unit is located.
According to another aspect of the present invention, there is
provided an image-forming apparatus, comprising the above moisture
data-acquiring device and an image forming assembly for forming an
image on a sheet, wherein a condition for image formation is
adjusted based on the data from the moisture data-acquiring
device.
An image-forming apparatus, comprising the moisture data-acquiring
device set forth in claim 1, an image forming assembly for forming
an image on a sheet and a delivery means for delivering the sheet,
wherein a condition for delivering sheet are adjusted based on data
from the moisture data-acquiring device.
As described above, a novel type of moisture data-acquiring device
can be provided according to the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic drawing for explaining the present
invention.
FIG. 2 is a schematic drawing for explaining an embodiment of the
present invention.
FIG. 3 shows steps of operation with the device of the present
invention.
FIG. 4 shows results of measurement with the above device.
FIG. 5 illustrates schematically a constitution, of a device of an
embodiment of the present invention.
FIG. 6 shows an output from the sensor equipped in the above
device.
FIG. 7 shows results of measurement with the above device.
FIG. 8 illustrates schematically a constitution of a device of an
embodiment of the present invention.
FIG. 9 illustrates an example of an image-forming apparatus
equipped with the device of the present invention.
FIG. 10 shows an output from the sensor equipped in the above
device.
FIG. 11 shows results of measurement with the above device.
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention is explained by reference to
FIG. 1.
In FIG. 1, force-applying unit 1000 applies an external force to
sheet 1050. Force-receiving unit 1010 receives the external force
through sheet 1050. A signal-outputting unit (not shown in the
drawing) which outputs a signal reflecting the mechanical property
of the sheet is provided on the side of the force-applying unit or
on the side of the force-receiving unit.
The information on moisture contained in the sheet is acquired from
the signal output from the signal-outputting unit by comparing the
outputted signal with a preliminarily memorized data in the
memorizing unit regarding the dependence of the outputted signal on
the water content in the sheet material.
The data (or information) on moisture contained in the sheet
includes a water content (%), an absolute quantity of water (g), a
change of the water content corresponding to a change of the
environment or handling history of the sheet material, and
distribution of the water in the sheet face direction and the sheet
thickness direction. In the present invention, the water content
(%), for a sheet weight A (g) and a water quantity B (g) in the
sheet, signifies the value of [B/(A+B)].times.100 (%). The absolute
quantity of water signifies a weight (g) of water contained in a
sheet of any size. In the description below, the term "moisture"
signifies the aforementioned information on water.
The principle of the present invention is described below
briefly.
An external force applied to a sheet material will decay under
action of the material of the sheet. The degree of the decay
depends on the mechanical properties including compression strength
and rigidity such as bending strength of the material of the sheet.
The sheet will change its mechanical properties depending on the
moisture quantity contained in the sheet.
Therefore, the data on moisture can be acquired from the
aforementioned outputted signal by comparison with a preliminarily
prepared chart or diagram memorizing the dependency of the
outputted signal on the moisture quantity or a relative equation
formula therefor.
For obtaining the moisture data, the external force may be applied
one time, or several times at a constant strength or several,times
with the strength varied.
In one preferred embodiment, the external force applied by the
force-applying unit bends the sheet to bring the sheet into contact
with the force-receiving unit, whereby a signal is outputted from
the signal-outputting unit. This embodiment is preferred since the
signal reflects not only the compression strength but also degree
of the bending of the sheet material. Incidentally, for bending of
the sheet material by the applied force, a concave or a groove is
provided on the impact-receiving side, which will be described
later specifically.
In another preferred embodiment, the moisture data-acquiring device
is mounted on an image-forming apparatus, and the moisture data is
utilized for setting the conditions for image formation on the
sheet in the image forming assembly (the conditions including an
ink ejection quantity from an inkjet system, a toner fixation
temperature in an electrophotograph system, etc.), or conditions
for delivering the sheet material by a sheet delivering means (the
conditions including a sheet delivery speed, a pressure between
pinching rollers for delivery of the sheet, etc.).
The aforementioned moisture data-acquiring device can be used
practically for a water content measurement.
The present invention is explained below more specifically by
reference to drawings.
FIG. 2 illustrates schematically constitution of a
moisture-measuring device of a first embodiment of the present
invention. In FIG. 2, force-applying unit 1 constituted of an
external force-controlling means is controlled manually,
automatically, or by a personal computer not shown in the drawing
to produce a prescribed dynamic force and to controls the dynamic
force. Force applying member 2 is driven by the force produced by
force applying unit 1 toward sheet 3, downward in this
embodiment.
Force-applying member 2 driven downward by the external force
produced by force-applying unit 1 comes to collide against sheet 3
placed below. In this embodiment, force-applying unit 1 utilizes a
motor, a cam, and a spring (not shown in the drawing) to allow
force-applying member 2 to collide against sheet 3 to apply the
external force thereto in every rotation of the motor.
Measurement table 4 as a sheet holding means holds sample sheet 3
at a measurement position. Measurement table 4 has rectangular
aperture 41 at the position confronting the force-applying member
2. This aperture 41 may be circular or ellipsoidal, the shape being
not limited. Force-applying member 2, when dropped, passed
through-aperture 41 to collide against force-receiving member 5
confronting aperture 41.
This movement of force-applying member 2 bends sheet 3 downward
through aperture 41 to collide against force-receiving member
5.
Pressure sensor 6 is placed in contact with the bottom face of
force-receiving member 5. On collision of sheet 3 against
force-receiving member 5 by action of force-applying member 2, the
impact force of the collision is transmitted through
force-receiving member 5 to pressure sensor 6. The pressure sensor
6 outputs an electric signal in correspondence with the transmitted
impact force.
Moisture-measuring unit 10 receives the electric signal from
pressure sensor 6, and detects the moisture in sheet 3 according to
the electric signal from pressure sensor 6.
The rigidity of sheet 3 depends on the moisture content. Therefore
at a fixed external force, the impact force transmitted by bending
or compression of sheet 3 depends on the moisture content of sheet
3. Accordingly, the moisture content can be measured, by
moisture-measuring unit 10, from the electric signal inputted from
pressure sensor 6 as an external force-detecting means for
detecting the impact strength transmitted through force-receiving
member 5 based on the impact force strength.
In this embodiment, moisture-measuring unit 10 measures the
moisture content in sheet 3 by comparing electric signal from
pressure sensor 6 with calibration table 11 prepared preliminarily
for the dependency of the electric signal on the moisture content
in sheet 3.
In FIG. 2, force-receiving member 5, pressure sensor 6, and damping
member 7 are bonded together by an adhesive to have a common center
line with force-applying member 2, and aperture 41 of measurement
table 4.
Pedestal 8 supports force-receiving member 5, pressure sensor 6,
and damping member 7. Damping member 7, although not essential, is
preferably provided to remove unnecessary vibration especially when
pressure sensor 6 may generate noise by the vibration. In FIG. 2,
the lead wiring is not shown.
In this embodiment, the periphery of aperture 41 serves as the
fulcrum for bending the sheet 3. Therefore, the size of the
aperture is preferably made changeable to meet the measurement
purpose. Further, the level difference between the face of
measurement table 4 for supporting sheet material 3 and the face of
force-receiving member 5 is preferably made changeable to meet the
purpose of the measurement. In other words, on application of an
external force to the sheet, the bending extent and compression
extent depend on the size of aperture 41 and the level difference
between the face of measurement table 4 and the face of
force-receiving member 5. Therefore, the aperture size is
preferably selected to meet sheet 3 to be measured.
The aforementioned level difference is not limited. However, when
the face of force-receiving member 5 is at the same level as or is
higher than the face of measurement table 4, the compression extent
of sheet 3 is defined. When the face of force-receiving member 5 is
lower than the face of measurement table 4, the bending extent and
compression extent of sheet 3 are defined. Therefore, when strong
external force is applied, the level difference is adjusted not to
cause breakage of sheet 3 or not to cause an irreversible change of
the physical property thereof. In other words, measurement table 4
and force-receiving member 5 are placed in a relative position to
define the deformation of sheet material 3 by the external
force.
Next, the moisture measurement steps with a moisture-measuring
device of the present invention are explained by reference to FIG.
3.
Firstly, sample sheet 3 is placed on measurement table 4 (Step 1).
Then, an external force is applied by force-applying unit 1 through
force-applying member 2 to sheet 3 (Step 2). For the external force
application, the strength, application time, frequency, and so
forth of the force are set by force-applying unit 1. This condition
setting may be made automatically by an external means such as a
personal computer not shown in the drawing.
On application of the external force, sheet 3 is bent to enter
aperture 41 of measurement table 4 together with force-applying
member 2 and collides against force-receiving member 5. The impact
is transmitted to pressure sensor 6. That is, the applied force is
transmitted through sheet material 3 (and force-receiving member 5)
to pressure sensor 6.
Pressure sensor 6, on receiving the applied external force as an
impact force through force-receiving member 5, outputs a detection
signal reflecting the mechanical properties of sheet material 3
(Step 3). Pressure sensor 6 constituted of a piezoelectric element,
for example, produces an electric signal.
The electric signal generated in the piezoelectric element is
inputted to moisture-measuring unit 10, where the electric signal
is compared with a preliminarily prepared calibration table 11
showing the dependence of the electric signal on the moisture
content in sheet material 3 (Step 4). The moisture content in sheet
material 3 is calculated (detected) by comparison of the electric
signal with the calibration table (Step 5).
The result of the calculation (detection) is displayed, recorded,
stored in a memory, or sent through the internet to complete the
measurement (Step 6).
FIG. 4 shows a calibration table for electrophotographic paper
sheets, FB75 (Fox River Bond Co.), as an example of sheet material
3. The calibration table shows the results of moisture measurement
by a moisture-measuring device of the present invention with the
paper sheets conditioned for 48 hours in a closed vessel kept at
the measurement temperature of 25.degree. C. and at controlled
humidity.
In the above measurement, force-applying member 2 was a stainless
steel round-column of 3 mm in diameter and 4 g in weight. Naturally
the tip of the member may be rounded. Force applying unit 1 was set
to allow force-applying member 2 to collide against the paper sheet
at a velocity of 0.48 m/s by utilizing a motor, a cam, and a spring
which are not shown in the drawing. The level difference between
the face of measurement table 4 and the face of force-receiving
member 5 was adjusted to 0.2 mm. Pressure sensor 6 employed was a
piezoelectric element. The moisture content was measured with a
paper moisture tester, Moistrex MX-5000E T80 (Shinmei General Co.).
In the description below, this paper moisture tester is simply
referred to a "paper moisture tester".
The output voltage from the piezoelectric element was found to be
in a linear relation with the moisture content measured by the
paper moisture tester as shown in FIG. 4. The regression line
therefor was represented by the equation: y=-0.25x+5.75 where x
represents the moisture content, and y represents the generated
voltage.
The moisture content in the FB75 paper sheet of unknown moisture
content can be determined by measuring the generated voltage and
conducting calculation according to the preliminarily prepared
regression line. For example, in the aforementioned moisture
measurement procedure, the generated voltage of 4.5 V shows a
moisture content of 5% according to FIG. 4. In the above
measurement, the time after contact of force-applying member 2 with
sheet material 3 to voltage generation by pressure sensor 6 is only
several milliseconds, so that the measurement including the
calculation of the moisture content by the regression line can be
completed within 0.1 second. Thus, the moisture measurement can be
completed in a short time by use of the moisture-measuring device
of this embodiment.
In FIG. 4, the generated voltage and the moisture content are in a
linear regression relation. In some cases, according to the kind of
sheet material 3 or conditions of external force application, the
relation is in a curved regression. In this case also, the moisture
content can naturally be detected by the same process. In the above
embodiment, the calibration table was prepared at 25.degree. C.,
but may be prepared in any temperature depending on the use or
purpose. Since the moisture content varies in accordance with the
atmospheric pressure, the regression function may be prepared at
different atmospheric pressure when the atmospheric variation may
cause a problem.
In the above explanation, force-applying unit 1 employs a cam and a
spring. Otherwise, force-applying member 2 may be allowed to fall
freely by use of a cam, or a solenoid may be used for the dropping.
The force applying means for the external force generation is not
limited at all.
The movement of force-applying member 2 toward sheet material 3 may
be a uniform movement, a uniformly accelerated movement, or a
random movement. The force may be applied to the sample sheet by
one motion or plural motions with confirmation of reproducibility.
Otherwise, the forces in different strengths may be applied, and
the moisture content may be determined from the respective
relations between the voltage for the strength of forces and the
moisture content.
Pressure sensor 6 is not limited to the aforementioned
piezoelectric element, but may be the one utilizing the
piezoelectric effect of a ferroelectric substance, a piezoelectric
substance, a pyroelectric substance, or a semiconductor substance.
Instead, the positional shift by an external force of a dielectric
substance placed between electrodes may be detected by measuring
electric capacity between the electrodes. Otherwise, a volume
change of a gas or a liquid may be measured optically. A strain
meter may be used. A velocity-measuring means for measuring a
velocity of a moving body such as a Doppler velocity meter may be
used for measuring the velocity change of force-applying member 2.
The pressure sensor utilizing a piezoelectric effect of a
piezoelectric element, a semiconductor, or the like is preferably
employed for a smaller size of the device. The most suitable one is
selected to meet the use and the object.
In the above explanation, the peak value of the voltage transmitted
from the piezoelectric element is measured. However, the electric
signal for the measurement is not limited to the voltage. Also
useful are a peak area intensity, a gradient of a voltage peak by
waveform analysis, and a voltage in a prescribed frequency region
obtained by frequency analysis. This frequency region is not
limited. An audible region can be employed.
Sample sheet 3 need not be flat, and may be creased or wrinkled.
For measurement of such a non-flat sheet, a mechanism for smoothing
sample sheet 3 or preventing wrinkle formation may be provided in
the device shown in FIG. 2. In some cases, the measurement may be
conducted with sample sheet 3 stretched horizontally in FIG. 2.
During the sheet delivery, sample sheet 3 may swing or vibrate. To
prevent this, a sheet-pressing mechanism may be provided to
suppress variation of the level difference between sample sheet 3
and pressure sensor 6 caused by the swing or vibration of the
sample sheet.
In FIG. 2, sample sheet 3 is shown to be flat. However, measurement
table 4 need not be flat. Measurement table may be curved and
sample sheet 3 may be curved correspondingly, provided that sample
sheet 3 is in stable contact with measurement table 4.
The strength of the force applied to sample sheet 3 is controlled
not to damage or break sample sheet 3. In a case where the
force-applied portion of the sheet should not be deformed
irreversibly, the force strength is adjusted to cause recoverable
elastic deformation, or to cause non-trouble-causing slight
deformation of sheet 3. The number of times of the force
application is not specially limited. When a motor and a cam are
employed, for example, the force may be applied plural times by the
cam shape. The plural forces may be applied at the same strength or
at different strengths. The force need not be applied
perpendicularly to sheet 3, but may be applied in any direction,
provided that the output from the sensor can be detected.
A second embodiment is explained below.
FIG. 5 shows schematically the constitution of moisture-measuring
device in this embodiment. In FIG. 5, the same symbols as in FIG. 2
are used for denoting the corresponding parts.
In FIG. 5, force-applying unit 1A has force-applying member 2, and
pressure sensor 6A constituting an external force-detecting means,
in integration. This force-applying unit 1A is allowed to fall
freely by a motor and a cam not shown in the drawing. In this
embodiment, main body 1B or the force-applying unit has been worked
as shown in FIG. 5. Pressure sensor 6A as a piezoelectric element
is fixed in a state of a beam on the upper face of main body 1B of
the force-applying unit.
The strength of the external force to be applied is adjusted by the
level difference between the tip of force-applying member 2 and the
face of measurement table 4. Naturally, the strength of the
external force may be adjusted by the distance between the tip of
force-applying member 2 and the face of the sample sheet 3 since
the external force depends on the thickness of sample sheet 3.
In this embodiment, force-applying member 2 is a round column of
Derlin with the tip end rounded. Force-applying member 2 need not
be made of a single material: for example, a metal part may be
attached to the tip. The shape is not limited to a round column,
but may be a prism, a sphere, or the like. Sample sheet 3 may be
kept stopped or moving. Measurement table 4 may be made of any
material including inorganic materials such as a metal, and a
ceramic; organic materials such as an ABS resin; and composites of
an organic material and an inorganic material. In measurement of a
sample sheet moving for delivery as in a copying machine, the
material of the measurement table is preferably selected which has
a suitable frictional coefficient for the purpose, since the
friction between the sample sheet and the table may cause a trouble
in the sheet delivery or image formation.
The moisture of the sample sheet is measured through the steps
below.
Firstly, sample sheet 3 is placed on measurement table 4.
Force-applying unit 1A is allowed to fall from a predetermined
height to apply an external force with force-applying member 2 to
sample sheet 3. The weight of force-applying unit 1A which is
constituted of force-applying member 2, main body 1B of the
force-applying unit, and pressure sensor 6A has been adjusted to a
prescribed weight. After force-applying unit 1A falls freely and
collides against sample sheet 3, force-applying unit 1A allowed to
rebound by rigidity of sample sheet 3, and to collide repeatedly
against sample sheet 3.
In the repeated collision of force-applying unit 1A, the repulsion
force (output) of sample sheet 3 acts on force-applying unit 1A to
output plural signals from pressure sensor 6A. For example, with an
inkjet recording paper sheet LC301 (Canon K.K.) as sample sheet 3,
plural electric signals are outputted from pressure sensor 6A as
shown in FIG. 6.
In FIG. 6, force-applying unit 1A collides about ten times against
sample sheet 3. In FIG. 6, the first to fifth voltage peaks are
numbered. The moisture content may be measured, for example, from
the generated voltage in comparison with the aforementioned
calibration table. However, in this embodiment, with the observed
first to n-th peaks, a calibration table is prepared regarding
dependence of the time from the first collision to the (n-m)th
collision (n-m.gtoreq.2) on the moisture content, and the moisture
content in sample sheet 3 is detected by comparison of the time
interval between the peaks with the calibration table.
In FIG. 6, for example, the fifth collision occurs 71 milliseconds
after the first collision. The moisture content is measured from
the time for the repeated collision.
FIG. 7 shows, as an example, the calibration tables for inkjet
recording paper sheets LC301 and HR101s (both from Canon K.K.). The
calibration tables are prepared, for the fall of force-applying
unit 1A of 8 g in weight from a height of 3 mm above the surface of
measurement table 4, by plotting the time from the first rebound to
the fifth rebound as the ordinate and the moisture contents
measured by a paper moisture tester as the abscissa. The
measurement is conducted at 25.degree. C. The moisture contents of
the paper sheets are measured (detected) after the paper sheets are
conditioned for 48 hours in a closed humidity-controlled
container.
FIG. 7 is useful as the calibration table measurement of the
moisture content of an unknown sample. For example, for the paper
sheet HR101s, the relation between the rebound time y
(milliseconds) in the ordinate and the moisture content x (%) in
the abscissa in FIG. 7 is represented by a regression line:
y=-8.1x+146.2 From this regression line, the rebound time of 100
milliseconds corresponds to moisture content of 5.7%.
Not only by the rebound time, the moisture content can be measured
by the voltage peak shape, the voltage peak breadth, the voltage
peak gradient, the voltage peak area, detection of specific
frequency band by frequency analysis, or the like or combination
thereof.
As described above, the moisture contained in a sample sheet can be
measured in a shorter time with a smaller-sized device by applying
a predetermined dynamic force onto sample sheet 3 and measuring the
output from sample sheet 3 in response to the applied external
force.
In the above explanation, the moisture measurement is conducted
based on the rigidity change of sample sheet 3 depending on the
moisture content. The present invention is not limited thereto. The
moisture content can be measured based on other dynamic properties
of sheet 3 varying as a function of the moisture content, such as
the Young modulus, the density, and sheet thickness.
Further, in the above explanation, an electric signal from a
pressure sensor (piezoelectric element) is utilized in the moisture
measurement. The present invention is not limited thereto. An
optical or magnetic output corresponding to the absorption,
propagation, amplification, or repulsion of the external force by
sample sheet 3 may be utilized for the moisture measurement (or
detection).
The present invention is explained more specifically by reference
to Examples. Incidentally, in Examples below, a piezoelectric
element is used as the pressure sensor, but is not limited thereto.
The materials for the constitution parts are not limited also.
EXAMPLE 1
Moisture was measured with a moisture-measuring device shown in
FIG. 2.
In this Example, force-applying member 2 was a stainless-steel
round column of 3.5 mm diameter, having a weight of 4 g adjusted by
controlling the length, and having a flat tip end. Measurement
table 4 for placing sample sheet 3 was a stainless steel plate of 2
mm thick, having rectangular aperture 41 of 10 mm.times.30 mm at
the center. Force-receiving member 5 was a stainless steel plate of
5 mm.times.5 mm and 1.5 mm thick. Piezoelectric element 6 had a
size of 5 mm.times.10 mm and 30 .mu.m thick. Damping member 7 was a
nitrile rubber of 5 mm.times.5 mm and 2 mm thick. The
force-receiving member 5, piezoelectric element 6, and damping
member 7 were bonded by an adhesive together and were placed so as
to have a center line common to aperture 41 formed in measurement
table 4.
Pedestal 8 for fixing force-receiving member 5, piezoelectric
element 6, and damping member 7 was a stainless steel plate of 7
mm.times.60 mm and 5 mm thick, and was fixed by screws not shown in
the drawing. The level difference between the face of measurement
table 4 and force-receiving member 5 was adjusted to 0.2 mm. The
electric signals from piezoelectric element 6 may be taken, for
example, by an oscilloscope or a general-purpose voltage detection
circuit (not shown in FIG. 2). In this Example, the electric
signals were introduced through a personal computer into an
oscilloscope, and the moisture content was calculated by a personal
computer (moisture detecting means).
Printer paper sheets FB75 (Fox River Bond Co.) were used as the
measurement sample. The paper sheets were kept for 48 hours in an
environmental test chamber of constant humidity at 25.degree. C.
Thereafter the moisture contents of the paper sheets after 48-hour
conditioning were measured by a paper moisture tester in the
environmental test chamber. The paper sheets after the moisture
measurement were set on the moisture-measuring device shown in FIG.
2.
Then instruction was outputted from a personal computer (not shown
in the drawing) to force-applying unit 1 to apply an external force
to paper sheet 3. The signals from piezoelectric element 6 were
detected by an oscilloscope, and the maximum voltage generated was
introduced through the memory of the oscilloscope to the personal
computer.
The measurement was conducted 20 times respectively with paper
sheets of various moisture contents by the above moisture-measuring
device and the paper moisture tester. The correlation of the
average of the voltage with the average moisture content is shown
in the aforementioned FIG. 4. The moisture content x and the
generated voltage y were in a linear relation as shown in FIG. 4,
the regression function being represented by the following
equation: y=-0.25x+5.75 This regression line was stored in the
memory of the personal computer as the calibration table.
After preparation of the calibration table, a paper sheet FB75 of
an unknown moisture content was placed on measurement table 4. An
external force was applied to the paper sheet (Steps 1 and 2). In
this Example, the external force was applied ten times repeatedly.
The voltages generated in pressure sensor 6 were found to be 0 volt
four times and 4.1 volts six times.
From comparison of the above results with the memorized regression
line as the calibration table, the moisture content was found to be
6.76%. The measurement error was .+-.0.2% estimated from the
variation of the detected voltage. The time for one measurement was
about 20 milliseconds after giving a signal of rotation to the
motor. Since the rotation rate of the motor was 50 milliseconds per
rotation, the time for the ten repetition of measurement was 0.5
second.
Paper sheets, FB75, having been conditioned at 25.degree. C. and
85% RH for 35 hours, and other paper sheets, FB75, having been
conditioned at 25.degree. C. and 15% RH for 24 hours were
transferred to an environment of 25.degree. C. 52% RH. Ten minutes
after the transfer, the moisture contents were measured. The paper
sheet conditioned at 25.degree. C. and 85% RH gave detected
voltages of 3.6 volts immediately after the transfer and 3.8 volts
3 minutes after the transfer. This showed that the moisture content
of the paper sheet became changed from 8.6% to 7.8%.
The paper sheet conditioned at 25.degree. C. and 15% RH gave
detected voltages of 5.1 volts immediately after the transfer and
4.7 volts 5 minutes after the transfer. This showed that the
moisture content of the paper sheet changed from 2.6% to 4.2%. The
moisture content values measured by an optical paper moisture
tester for the same environmental change as above agreed with the
above measurement results within an error of about 0.1%. The time
for one measurement by the optical paper moisture tester is about 2
to 3 seconds, thus ten measurements requiring 20 seconds or more in
total. Therefore, the moisture-measuring device of this Example can
shorten the moisture measurement time.
Incidentally the materials of the sheets of the object of the
present invention are usually composed mainly of cellulose. In
measurement of the moisture of a cellulosic material by an optical
means like a spectroscope, the cellulose causes two types of light
absorption: absorption by oxygen-hydrogen bonding in the cellulose,
and absorption by oxygen-hydrogen bonding of the moisture contained
in the sheet material. Therefore, in the measurement of the light
absorbance, the above two types of absorption should be
discriminated. Accordingly, optical measurement of the moisture
requires measurement time of several seconds generally.
EXAMPLE 2
Moisture was measured with a moisture-measuring device shown in
FIG. 8.
The moisture-measuring device shown in FIG. 8 employed
force-applying member 1A shown in FIG. 5 in place of force-applying
member 1 shown in FIG. 2. With force-applying member 1A shown in
FIG. 5, the external force applied to sample sheet 3 could be
detected by piezoelectric element (pressure sensor) 6A provided
with force-applying member 2 on force-applying unit 1A on the upper
side of sample sheet 3 as well as by piezoelectric element
(pressure sensor) 6 placed at the bottom of force-receiving member
5.
In this Example, the moisture content can be measured by either one
of piezoelectric elements 6 and 6A or the both thereof. However,
with the upper piezoelectric element 6A, the moisture content is
preferably measured by the rebound time rather than the generated
voltage. With the lower piezoelectric element 6, the moisture
content may be measured by any of the rebound time and the first
voltage peak.
If the moisture contents measured by the two piezoelectric elements
6 and 6A are different significantly from each other, the
measurement is considered to be erroneous. Thus the preciseness of
the measurement can be judged by comparison of the two measurement
results.
In this Example, the upper piezoelectric element 6A had a size of
1.5 mm.times.25 mm and 0.4 mm thick. Force-applying unit 1A was 8 g
in weight and made of brass. Force-applying member 2 was a
stainless-steel round column of 4 mm diameter, having conical top
portion with a flat tip end of 1 mm.sup.2 in area.
In FIG. 8, the numeral 9 indicates a brass block having a size of
10 mm.times.10 mm.times.30 mm. In this Example, two blocks 9 were
employed as a pressing mechanism for pressing sample sheet 3. After
setting sample sheet 3, blocks 9 were placed manually at positions
nearly symmetrically to aperture 41.
Measurement table 4 for placing sample sheet 3 had an ellipsoidal
aperture 41 having a major axis of 30 mm and a minor axis of 15 mm.
Force-receiving member 5 having a top face convexing upward,
piezoelectric element 6, and damping rubber 7 were fixed on
pedestal 8 to have a center line common to aperture 41.
The level difference between the face of measurement table 4 and
the top of force-receiving member 5 was 0.3 mm. Force-receiving
member 5 had a size of 7 mm.times.10 mm. FIG. 8 shows a view taken
from the 7-mm side of the force-receiving member. The
force-receiving member 5 had a convex end face of a curvature of 90
mm diameter, and the maximum thickness of 2.5 mm. Piezoelectric
element 6 had a size of 7 mm.times.10 mm and 0.3 mm thick. Damping
rubber 7 was made of silicon rubber of 7 mm.times.9 mm and 2 mm
thick.
Force-applying unit 1A was allowed to fall freely from a height of
4 mm above measurement table 4. FIG. 6 mentioned before shows the
output from piezoelectric element 6A. In this measurement, the
temperature was 25.degree. C. and the humidity was 58% RH. Sample
sheet 3 was an inkjet recording paper sheet LC301 (Canon K.K.).
Force-applying unit 1A rebounded from the sample sheet and collided
against it repeatedly. Correspondingly, piezoelectric element 6A
outputted plural voltage peaks as shown in FIG. 6.
In this Example, the time from the first voltage peak to a
prescribed order number of the peak was measured since a low
rigidity of piezoelectric element 6A may cause deformation during
falling. In this Example, the time from the first peak to the fifth
peak was measured. The fifth voltage peak was observed 71
milliseconds after the first voltage peak.
On application of an external force to sample sheet 3 by
force-applying unit 1A (or force applying member 2), a voltage was
generated by piezoelectric element 6 as well as by piezoelectric
element 6A. In this measurement, the output voltage is basically
similar to that shown in FIG. 6. With a sheet of LC301, the voltage
generated by piezoelectric element 6 was observed to be about half
that of piezoelectric element 6A, and only three peaks were clearly
observed.
On the other hand, the calibration table showing the relations of
the moisture content and the signal voltage were derived for the
inkjet recording paper sheets C301 and HR101s as below.
The objective sample sheets, the moisture-measuring device of the
present invention, and a commercial paper moisture tester were kept
at 23.degree. C. for 48 hours in an environmental test room in
which the humidity is controllable.
Thereafter, the sample sheets were subjected to measurement with
the moisture-measuring device to detect the generated voltage of at
least one of piezoelectric elements 6 and 6A. In the measurement
with piezoelectric element 6A, the time from the first rebound to
the fifth rebound was measured. Separately the moisture content was
measured by the paper moisture tester. This test was repeated by
changing the humidity of the environmental test room to obtain the
correlation of the rebound time with the moisture content as shown
in FIG. 7.
In the above measurements, the two kinds of the sample sheets gave
respectively a linear regression relation. The rebound time y
(milliseconds) was a function of the moisture content x (%) as
shown by the linear regression equation: y=-4.7x+99 for LC301
y=-8.1x+148.9 for HR101s
In measurement with piezoelectric element 6, the first peak voltage
y (millivolts) was a function of the moisture content x (%) as
shown by the linear regression equations: y=-4.6x+7.9 for LC301
y=-8.1x+21 for HR101s The above relations were utilized as the
calibration table.
Paper sheets, LC301 and HR101s, having been conditioned in various
environments were subjected to measurement with the
moisture-measuring device of the present invention and with the
paper moisture tester, and the measurement results were
compared.
Consequently, the results according to the two measurement methods
agreed within error of .+-.0.1% for the sample sheets conditioned
in 20 different environmental conditions (temperature: 20
28.degree. C., humidity: 10 85% RH) for 48 hours. For example, the
sample sheets of LC301 and HR101s kept at 23.degree. C. and 85% RH
were found to contain moisture of 8.5% and 8.7% respectively by the
moisture-measuring device of the present invention, and 8.5% and
8.8% respectively by the paper moisture tester.
In the above measurement, the external force was applied by one
free falling of the force-applying member. The required measurement
time was 0.15 second or less for HR101s with piezoelectric element
6, whereas with the paper moisture tester, one measurement took a
time of 2 to 3 seconds.
The measurement errors with the piezoelectric elements 6 and 6A
were not larger than 0.1% for the sheets LC301, and HR101s.
Incidentally, for comparison, an LC301 sheet was crumpled by hands
to cause wrinkles and was subjected as it was to the measurement.
As the results, the measured values by piezoelectric elements 6 and
6A were different by 10% or more, showing the measurement result
not to be reliable.
EXAMPLE 3
The moisture-measuring device shown in FIG. 2 is mounted on an
image-forming apparatus such as a copying machine, an LBP, and an
inkjet printer.
FIG. 9 illustrates constitution of a portion of an image-forming
apparatus having a moisture-measuring device of the present
invention and an image-forming assembly not shown in the drawing
for forming an image on sheet 3. In FIG. 9, the symbol 4A denotes a
sheet delivery table of a sheet delivery system of the
image-forming apparatus. Sheet 3 is delivered at a prescribed speed
along the upper face of this sheet delivery table 4A. Sheet
delivery table 4A has aperture 41,. The shape of the aperture is
not limited, and may be circular, ellipsoidal, or corner-rounded
pentagonal, provided that the aperture does not interfere with the
delivery of sheet 3.
The numeral 20 denotes rollers for delivering sheet 3. Rollers 20
are not limited at all in the set position, the shape, and the
material. In FIG. 9, two pairs of rollers 20 are employed for
delivery of the sheet, but are not limited thereto. The external
force may be applied to the sheet delivered by either one pair of
rollers. Incidentally a mechanism for preventing flutter of the
sheet may be provided between the pairs of rollers.
In this Example, the start of delivery of sheet 3 from a sheet tray
(not shown in the drawing) of the image-forming apparatus is
confirmed by a sensor (not shown in the drawing). After a
prescribed time from the confirmation of the start of the sheet
delivery, force-applying unit 1 drives a motor to move
force-applying member 2 by a cam and a coil spring to apply a force
to sheet 3. In this Example, the cam is designed to apply the force
twice in one rotation of the motor, first strongly and second
weakly.
Force-applying member 2 is a stainless-steel round column having a
conical tip portion with a flat tip end face of 1 mm.sup.2 in area
as shown in FIG. 9, and having a weight of 4.8 g. The coil and the
cam not shown in the drawing were designed so that force-applying
member 2 impacts sheet 3 at a rate of 0.48 m/s, and 0.24 m/s.
Force-receiving member 5 is made of stainless steel having a convex
top face, having a maximum thickness of 4 mm and a size of 5
mm.times.7 mm. The level difference between the apex of the convex
of force-receiving member 5 and the lower face of sheet 3, or the
face of sheet delivery table 4, is 0.2 mm. Piezoelectric element 6
has a size of 5 mm.times.7 mm and 50 .mu.m thick. Damping member 7
is made of silicone rubber, having a size of 5 mm.times.7 mm and 2
mm thick.
With the above constitution, A4-sized recording paper sheets FB75
(Fox River Bond Co.) were delivered at a delivery rate of 50 sheets
per minute. Force-applying member 2 was brought into contact with
the FB paper sheets twice. The output from piezoelectric element 6
was detected by a voltage-detecting circuit (not shown in the
drawing). Thereby two voltage peaks were observed as shown in FIG.
10.
In FIG. 10, the first peak corresponds to the voltage generated on
contact of force-applying member 2 with the FB 75 sheet at a rate
of 0.48 m/s, and the second peak corresponds to the generated
voltage on contact at a rate of 0.24 m/s. FIG. 11 shows the
correlation of the peak voltage with the moisture content.
The voltage y (V) and the moisture x (%) were in the relation of
the regression function below: y=-0.22x+6.83 at the first time
y=-0.63x+4.63 at the second time
In the second force application in which the applied force is weak,
the voltage is not generated in a higher moisture content range.
However, as understood from FIG. 11, the steep gradient of the
regression line of the second force application enables observation
of slight moisture content variation in comparison with the first
force application.
In the above measurement, the paper sheets were kept at a
temperature of 23.degree. C. for 48 hours in a humidity-controlled
environmental test room before the measurement. Even when the
moisture-measuring device was brought into the environmental test
room immediately before the measurement, the measurement results
were not affected significantly by the temperature difference of
not more than 15.degree. C. Incidentally the linear regression
relation was memorized preliminarily in the memory (not shown in
the drawing) in the image-forming apparatus.
The moisture-measuring device of this Example was installed in
front of registration rollers of an image-forming apparatus.
A-bundle of 300 paper sheets was stored in a sheet tray. With this
apparatus, the same printing was conducted repeatedly at a printing
rate of 50 sheets of FB75 paper per minutes in six lots of 50
sheets at lot intervals of 5 minutes. Before and during the
printing, the apparatus was kept at 23.+-.2.degree. C. and 10 13%
RH. The moisture content of the recording paper sheets was 4.1%
immediately after taking out from a package bag as measured by a
paper moisture tester.
In the printing experiment, firstly, printing was conducted without
operation of the moisture-measuring device under constant printing
conditions (toner transfer voltage: 8 kV, fixation temperature:
190.degree. C.) in lots of 50 paper sheets at lot intervals of 5
minutes. During the printing, the ratio of toner transfer onto the
paper sheets became lower at the third and subsequent lots to cause
printing failure. At the time of the printing of the third lot, the
moisture content of the FB75 paper sheet was 3.2% as measured by
the paper moisture tester. Thus the moisture content was found to
have decreased after unsealing of the paper package bag.
Next, before starting the toner transfer onto the printing paper
sheet, the moisture content of the printing paper sheet was
measured by the moisture-measuring device, and the toner transfer
voltage was adjusted to meet the measured moisture. Prior to this
measurement, the correlation between the paper moisture and the
optimum transfer voltage had been derived preliminarily and had
been memorized in the memory unit of the image-forming
apparatus.
Thereafter, a bundle of 300 sheets of FB75 paper was taken out from
a package and was placed in a recording paper sheet tray. The
printing was conducted in lots of 50 sheets at lot intervals of 5
minutes. The environment of the image-forming apparatus was the
same as above. Of the printing conditions, only the toner transfer
voltage was adjusted to meet the measured moisture. Thus, the
printing could be conducted with all of the 300 sheets without
printing failure.
The change of the moisture content was monitored with the paper
moisture tester. The moisture changed from 4.2% at the first
printing lot, to 3.1% at the third lot, and 2.8% at the sixth lot.
The toner transfer voltage was changed in correspondence with the
change of the moisture content: 1.8 kV for the first lot, 2.5 kV
for the third lot, and 2.8 kV for the sixth lot. Thereby the
transfer failure could be prevented, whereby printing failure could
be prevented.
In the above-described printing, since the moisture content was in
a lower region, the regression line for the second
force-application was used. When the moisture content is higher to
lower the generated voltage on the second force-application or to
make the voltage unobservable, the regression line for the first
force-application is useful naturally.
In the image-forming apparatus of the present invention, the
printing is conducted at 0.2 second after passage of the recording
paper sheet through the registration rollers, whereas the moisture
can be measured within 0.1 second as shown in FIG. 10. Therefore
the moisture can be measured without stopping the sheet delivery
and without decreasing the printing speed.
This application claims priority from Japanese Patent Application
No. 2004-169114 filed Jun. 7, 2004, and Japanese Patent Application
No. 2005-146036 filed May 18, 2005 which are hereby incorporated by
reference herein.
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